I had my dealer mount Carlisles AG's 23x10.5x12 on my rear rims. The third number is the wheel size, not the width of the tire. The 2500's use 12 inch rear wheels, 8s up front. I replaced my stock 10s and 6s rear/front respectively on my 2180. The 23x10.5x12s will fit your 2500. They work on mine, although, I do lose the 6th deck setting as they rub against the 42" deck I have.